katalisator

A katalisator, or catalyst, is a substance that increases the rate of a chemical reaction without being consumed in the overall process. It does this by providing an alternative reaction pathway with a lower activation energy, so more reactant molecules can reach the transition state and form products.

Catalysts are commonly classified by their phase: homogeneous catalysts operate in the same phase as the reactants, while heterogeneous catalysts work in a different phase, usually a solid catalyst with gas or liquid reactants. Enzymes are biological catalysts, or biocatalysts, that accelerate biochemical reactions under mild conditions with high specificity.

The mechanism of catalysis often involves adsorption of reactants on active sites on the catalyst surface, formation of reaction intermediates, and desorption of the products. Catalysts can be highly selective, steering reactions toward a desired product and reducing side reactions. This property is crucial in producing fine chemicals and in energy-related processes.

Industrially important examples include iron catalysts with promoters for ammonia synthesis, platinum-group metal catalysts in catalytic converters to reduce emissions, and zeolites used in petroleum cracking and refining. Other catalysts, such as nickel or platinum for hydrogenation, are common in chemical manufacturing.

Catalysts face challenges such as poisoning by impurities, deactivation through sintering or coking, and sensitivity to temperature. Regeneration, proper reactor design, and catalyst engineering aim to maximize activity, selectivity, and durability. The study of catalysis underpins advances in sustainability, energy efficiency, and environmental protection.